Medical sampling ports are devices that allow a sample of fluid to be withdrawn, typically into a sampling vial. Typical sampling ports are tubular with one end closed to form a base and the other end open. A cannula is centrally mounted on the base and extends within the port toward the open end. The end of the cannula ends short of the end of the sampling port and so is not exposed. A sampling vial may be passed into the open end and impaled on the cannula.
It is desirable that the sampling vial when inserted into the sampling port is prevented from significant sideways movement, as this may result in damage to the cannula or incomplete penetration of the cannula into the sampling vial.
Sampling vials generally come with portions to be inserted in to a sampling port in two different maximum diameters. It is desirable that these different diameters are readily accommodated by the sampling port without the need for separate guides or the like that are inserted or removed from the sampling port to accommodate the different diameters.